Prosthesis for large blood vessels

ABSTRACT

A prosthesis for large blood vessels comprises a main conduit ( 2 ), at least one tract of which is subdivided into a plurality of small conduits ( 3 ) located parallel one to another.

TECHNICAL FIELD

The invention relates to the field of prostheses used in treatment ofthoracic-abdominal aneurysm.

BACKGROUND ART

The thoracic-abdominal aneurysm is largely a progressive yielding, fatalupon breaking, of the walls of the thoracic and abdominal aorta. Asthere is no possible medical therapy available, the pathology can onlybe treated by surgical intervention, which involves a large-scalethoracic laparotomy and substitution of the dilated tract with astraight tubular prosthesis. The visceral blood vessels and sometimesthe intercostal arteries are connected to the prosthesis.

The surgical operation is carried out usually according to two maintechniques, often used in combination.

The first of these techniques, also known as the De Bakey method,involves clamping (hemostasis) of the tract of aorta downstream of theaneurysm, a first sectioning of the aorta itself and the suturing of theprosthesis to the first section, and the clamping of the tract of aortaupstream of the aneurysm, a second sectioning of the aorta and thesuturing (anastomosis) of the prosthesis to the second section. Then thevisceral branches are sutured to the prosthesis with or withoutinterpositioning of prosthetic segments. This technique exposes thepatient to quite long operations with relevant haemhorraging, butguarantees good blood circulation downstream of the aneurysm.

The second technique, also known as the Crawford method, is based on thespeed of performance of the operation. The aorta is clamped upstream anddownstream of the aneurysm. The aorta is sectioned upstream anddownstream of the aneurysm, hemostasis is performed on any arteriesconnected to the sectioned tract of aorta, and the prosthesis is appliedwith rapid suturing to the two sections.

The visceral and intercostal arteries from the sectioned tract of aortaare then sutured to the prosthesis, preferably without interpositioningof prosthetic segments in order not excessively to extend operationtime. The technique implies that during the operation the circulationdownstream of the thorax is practically stopped. If possible, inanastomosis of the visceral and intercostal arteries, patches of aorticsections surrounding the original connection points of the arteries arere-used.

Although the results obtained using the techniques are satisfactory in amajority of the cases, with the patients' progressing to full recovery,there are however not inconsiderable risks connected to the importanceof the surgical operation itself.

The rate of mortality during or immediately following surgery, togetherwith post-operational respiratory difficulties and kidney failure, canreach up to 20%.

There is also a risk of about 20% of paraplegia, leading many patientsto refuse to undertake the operation.

Paraplegia, as well as the other complications, is essentially due to ablockage in arterial circulation to the lower parts of the body. Thisblockage, which is of a length correlated to the difficulty ofperformance of the operation, can obviously lead to medullar ischemiaand therefore to paralysis of the lower limbs.

To limit the risk of paraplegia temporary aortic by-passes are used,with extracorporeal circulation tubing taking blood from upstream of theaneurysm and sending it to the lumbar and hypogastric arteries. Theinflow of blood to these arteries guarantees a sufficientvascularization of the medulla and the abdominal organs, veryconsiderably reducing risks of ischemia. The use of extracorporealcirculation, however, involves considerable use of anticoagulants,especially if a pump is used, as is sometimes the case; in all cases,however, long operation times are needed.

The main aim of the present invention is to provide a prosthesis forlarge blood vessels which limits operation times for treatment ofthoracic-abdominal aneurysm, thus also reducing duration of hemostasisin the aorta.

A further aim of the present invention is to maintain the bloodcirculation downstream of the aneurysm during the anastomosis operationon the various blood vessels branching off from the affected tract.

DISCLOSURE OF INVENTION

Further characteristics and advantages of the present invention willbetter emerge from the detailed description that follows of a prosthesisfor large blood vessels, in a preferred but non-exclusive embodiment ofthe invention, illustrated purely by way of a non-limiting example inthe accompanying figures of the drawing, in which:

FIG. 1 is a perspective view of a prosthesis according to the presentinvention;

FIG. 2 is a first example of use of the prosthesis of FIG. 1;

FIG. 3 is a second example of use of the prosthesis of FIG. 1;

FIG. 4 is a third example of use of the prosthesis of FIG. 1;

FIG. 5 is a fourth example of use of the prosthesis of FIG. 1.

With reference to the figures of the drawings, 1 denotes in its entiretya prosthesis according to the present invention. It comprises a mainconduit 2, at least a tract of which is subdivided into a plurality ofsmall conduits 3 located parallel to one another.

The small conduits 3 each exhibit an internal calibre which is smallerthan the main conduit 2 and the overall section of the small conduits 3is about the same as that of the main conduit 2. The flow of bloodentering the main conduit 2 is sub-divided into the small conduits 3.

The small conduits 3 are also independent of one another. They exhibitlateral walls which are distinct one from another, so that they can bemanipulated and used separately. The small conduits 3 are for examplethree in number, one of which may exhibit a larger calibre than theremaining two thereof

The main conduit 2 and the small conduits 3 are made of a bio-compatiblematerial which has only a small elastic deformability in a transversaldirection and a considerable elastic deformability in a longitudinaldirection.

The application of the prosthesis of the present invention can be madein the following stages.

After having approximated the length of prosthesis required, distalclamping is performed and distal anastomosis 10 a to the aorta 10 iscarried out. Subsequently proximal clamping is performed and theaneurysm opened with clamping of the branching vessels in the tractaffected by aneurysm. Proximal anastomosis 10 b is then performed. Oncethe two suturing operations have been carried out, the clamps can beremoved and abdominal and medullar blood circulation restored.

In this calm situation the anastomosis of the branch vessels 12 from thetract subject to aneurysm can be carried out; the branch vessels 12 aresutured to the prosthesis while blood circulation is maintained throughthe other small conduits 3. As can be seen in FIG. 2, the branch vessels12 can be sutured with the use of small patches 11 of original aorticmatter surrounding the ends of the vessels and cut away with the vesselsthemselves. These can be sutured onto the largest of the small calibreconduits 3. If this technique is not possible, the small calibreconduits 3 can be used for end-to-end anastomosis between the prosthesisand the branch vessels 12 originating from the tract affected byaneurysm, while circulation is maintained through the small conduit 3 oflargest calibre (FIGS. 3, 4, 5). Alternatively a small conduit 3 can beused to create a temporary by-pass of the prosthesis itself.

The application of the prosthesis of the present invention guarantees ahigh degree of liberty of action to perform the required anastomosis,whether pre-determined or decided during the course of the actualoperation.

The duration of the hemostasis is thus limited to the time required forcarrying out the proximal and distal anastomosis of the prosthesis tothe aorta, reducing by a very considerable degree the risk of medullaror abdominal ischeria.

1). A prosthesis for large blood vessels, wherein the prosthesiscomprises a main conduit (2), at least one tract of which is subdividedinto a plurality of small conduits (3) located parallel one to another.2). The prosthesis of claim 1, wherein the small conduits (3) each havean internal calibre which is smaller than an internal calibre of themain conduit (2). 3). The prosthesis of claim 2, wherein an overallsection which is a sum of sections of the small conduits (3) isapproximately equal to a section of the main conduit (2). 4). Theprosthesis of claim 3, wherein the small conduits (3) are independentone from another. 5). The prosthesis of claim 2, wherein the smallconduits (3) are three in number. 6). The prosthesis of claim 5, whereina small conduit of the small conduits (3) exhibits a greater calibrethan two of the small conduits (3). 7). The prosthesis of claim 6,wherein the main conduit (2) and the small conduits (3) are made of abio-compatible material which exhibits a small elastic deformability ina transversal direction thereof and a greater elastic deformability in alongitudinal direction thereof